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making 2 1x15" cabs- low end response Q

Discussion in 'Amps and Cabs [BG]' started by black_labb, Mar 4, 2008.


  1. hi guys, im new to this forum. ive picked up 2 15" drivers cheaply (got 2 of these for 30$ each when they were on special. i wasnt really looking to get 15" speakers, but at that price i couldnt pass up the opportunity. you probably havent heard of the brand, but they have become pretty popular with builders of guitar amps as they make some great vintage style speakers. i started building guitar amps a year ago so i heard a bit about them.

    im on a bit of a budget, so ill probably make them from mdf, and cover them in a material i saw at the hardware store (similar to vinyl, but a bit thicker. im planning to put 2 wheels on a corner, and lift the other side up so it can be wheeled (like those suitcases that have an extendable handle). it should work well, as the cab will be longer, making it a rectangular prism as opposed to cubic looking.

    im planning on making a sealed cab first, and then making a second later that will probably be a ported one.

    my main questions is, what kind of decibel level should i aim for at the 40 hz? ive been using winisd to calculate the decibel response with the cab, and the current design for the cab, the response at 41hz is -8.5 db. i know that most manufacturers put incorrect readings for the -3db mark, but is this a reasonable level? i know i wont get as much bass sensitivity on a sealed cab, but it still seems low to me. increasing the volume from 130 to 200 doesnt make a big difference either, its only when you port the design that you get closer to the 3db point. what kind of level do you guys usually design for? the amp ill be using is an australian made 200w guitar amp from the 70's running on 4 6550 tubes. i changed the value of some of the cathode bypass caps to get some more low end out of it.

    ill be playing a 4 string, but will be playing a 5 aswell once i finish making it (i make basses and guitars as well) that i will probably tune up a half step from b. im not too sure how important the low end will be. im mainly a guitarist, who is getting quite interested in bass after listening to alot of nomeansno. ill be playing in a trio where ill be plaing bass, and the singer (my girlfriend) will be playing guitar with a slide almost exclusively. i want to be more into the mids than most bassists, so im not sure if the 15" drivers are the best idea. would you guys think that the 15" would work alright for me, or do you think i should make the cabs with the intention of selling them after a bit to fund a 4x10 or trade?


    sorry for the meandering thread, i know i need to figure some things out myself as well. if you have any advice id apreaciate it.

    thanks

    thanks for any help, i
     
  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    There's a point of diminishing returns on box volume. This speaker has a stiff cone (suggested by relatively high Vas value). It's not going to have huge low end.

    I think it's worth looking into doing a ported box right away. It's not prohibitively difficult.
     
  3. i may just do the ported design, with the same size as the sealed one i was going to do. i was going to do the ported design at 200L volume, but that just seems rediculous to me for a 1x15. just measured the dimensions against a cabinet in my room, and found that 200L would be the same size. could probably fit a 6x10 in that.
    i ordered some mdf for it (precut to save me some work, and it came out cheaper than i expected, but i had no idea how much it would be anyway). i may try it without the ports, then add them in, more as a way of checking the differences for my own understanding.


    another question, reguarding the ports. when you measure the size of a port, do you measure the length as the internal length of the port from where it starts within the cab to where it finishes outside, or is it how far it protrudes into the cabinet? essentially i want to know wether to measure from the front of the baffle (exterior) or the inside of the baffle. it seems to me that it would be from the exterior of the baffle, but i just want to check.

    am i right in finding some suitable plywood for the baffle, as mdf would not take a threaded insert very well?

    thanks for the help
     
  4. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The port measurements are the internal length and diameter.

    200 liters is big.
     
  5. Hi, black_labb.

    Welcome to the TalkBass.

    200l MDF cab will be a bit ;) bulky and heavy, I'd aim a bit lower to the point of a diminishing returns on box volume as fdeck suggested.

    Ported is the way to go and allthough the low end won't most likely be anything spectacular, those cabs will probably double well as the PA bottoms paired with some smallish active cabs.

    Making DIY cabs for financing another purchases won't IMHO work well unless You're professional woodworker and have some reputation already. Not to mention getting the materials at discount prices.

    IME 2 1*15 cabs come handy in various situations and are a fine addition to any stack.

    MDF isn't IME that much cheaper than plywood to justify using it in cab-making.

    Do post some progress shots.

    Regards
    Sam
     


  6. i didnt know wether the mdf is cheaper, but it came out at 35$ australian cut to size. i thought that was good, as materials are usually quite expensive in australia compared to overseas. ill find out when i figure the price difference out where i can find some high quality ply for the baffle.

    im not too worried about weight, as i think the arrangement of the castors on the side, with a handle on the other, for wheeling on an angle should make it quite manouverable. may even allow it to be pulled up stairs without too much effort.

    reguarding using one of the cabs to finance another, i was more thinking of trading with someone for a beat 4x10 or something. torn vinyl doesnt worry me, adds character.
     

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